Rotational speed detector with ripple compensation

ABSTRACT

The rotary detector according to this invention comprises a rotary detector unit C 1 , C 1′  which detects rotary motion of a rotor; and a rotary calculator unit C 2 , C 2 ′, C 2 ″ comprising a rotation angle detector, which detects the rotation angle of the rotor, and an angle speed detector  47  which detects the angle speed of the rotor, based on the output of the rotary detector unit. The rotary calculator unit comprises a trigonometrical calculator C 3 , C 3 ′, C 3 ″ which calculates a sine value or a cosine value of the rotation angle detected by the rotary detector; a gain adjuster  57, 57′, 57 ″ which multiplies the sine value or the cosine value, calculated by the trigonometrical calculator, by a predetermined gain; a multiplier  59, 59′  which multiplies the output of the gain adjuster by the output of the angle speed detector; and a subtracter  61, 61′  which subtracts the output of the multiplier from the output of the angle speed detector.

This application is a 371 of PCT/JP02/095 15 filed Sep. 17, 2002 whichclaims benefit of Japanese patent 2001-280030 filed Sep. 14, 2001.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a rotary detector which can reduce thetorque ripple of a rotor and the like by reducing the ripple componentof an output signal.

2. Description of the Related Art

The output torque of a motor generally contains ripples. Since torqueripples are caused by speed irregularities and positional displacementof the support motor, they adversely affect the processing precision in,for example, an NC (numerical control) apparatus, and spoil thesmoothness of an elevator ride by increasing carriage shaking.

When detecting this type of torque ripple, the torque ripple may beinternal, arising in the motor main body comprising an accelerator, orexternal, arising in a rotary detecting sensor. Internal torque arisesfrom the work precision of a motor stator and a rotor, eccentricity ofthe rotor bearing, a high-frequency magnetic field inside the motor, andthe assembly precision of the decelerator. Many conventional methodshave been proposed for reducing torque ripples of the former type. Forexample, Japanese Patent Application No. 7-129251 centers on the torqueripple generated by a decelerator, and calculates a correction signalTcomp (=A·sin (θ+á1) where A is the torque ripple adjustment gain, θ isthe angle of rotation of the decelerator, and á1 is the initial phase;in synchronism with the rotation cycle of the motor, this signal is fedforward and added to the target torque command, thereby canceling thetorque ripple. Japanese Patent Application No. 11-299277 proposesstoring the correlation between the torque ripple and the angle ofrotation of the motor in a memory apparatus, reading a torque ripplecorresponding to the angle of rotation of the motor, and creating a newtorque command value by subtracting the ripple portion from the torquecommand value.

Since torque ripples of the latter type in the rotation detecting sensormentioned above appear as motor torque ripples, the ripple problem canusually be reduced by applying a control method, such as the onedescribed above, in the apparatus which controls the motor. However,when the ripples are caused by the angle of rotation being detected inthe output value of the rotation detecting sensor, the amplitude of theripples becomes larger in proportion to the detected angle speed,leading to a problem that it becomes impossible to increase the anglespeed feedback gain when controlling the torque of the motor and therotation speed; this places an enormous burden on the control apparatusand increases the cost of the apparatus.

In this way, a variety of control methods have been applied in thecontroller and driver of the rotating machine in conventional rotarydetectors, in an attempt to ensure that a ripple in the output does notbecome a torque ripple and speed irregularities of the rotating machinewhich the rotary detector is installed in. For this reason, thecontroller and driver of the rotating machine become complex, loweringits reliability and increasing the cost. Furthermore, in addition toripples in the output of the rotary detector, torque ripples in anelectric motor include those generated by assembly precision of thedecelerator, processing precision of the motor main body, high-frequencymagnetic fields and the like, making it difficult to determine the causeof the ripples in the output of the rotary detector, and undermining itsperformance as a sensor.

The present invention has been realized based on the circumstancesdescribed above, and aims to provide a rotary detector which can reduceoutput ripples, eliminate torque ripples and speed irregularities of anactuator, such as a rotating machine, which the rotary detector isinstalled in, simplify the driver and controller of the actuator, reducecosts, and increase reliability.

In order to achieve the above objects, the rotary detector according toa first aspect of this invention comprises a rotary detector unit whichdetects rotary motion of a rotor; and a rotary calculator unitcomprising a rotation angle detector, which detects the rotation angleof the rotor, and an angle speed detector which detects the angle speedof the rotor, based on the output of the rotary detector unit. Therotary calculator unit comprises a trigonometrical calculator whichcalculates a sine value or a cosine value of the rotation angle detectedby the rotary detector; a gain adjuster which multiplies the sine valueor the cosine value, calculated by the trigonometrical calculator, by apredetermined gain; a multiplier which multiplies the output of the gainadjuster by the output of the angle speed detector; and a subtracterwhich subtracts the output of the multiplier from the output of theangle speed detector.

According to a second aspect of the invention, in the rotary detector ofthe first aspect, the trigonometrical calculator comprises a phaseadjuster which adjusts the phase of the rotation angle, detected by therotation angle detector.

According to a third aspect of the invention, in the rotary detector ofthe first aspect, the rotary detector unit comprises a resolver whichcreates an output in accordance with the rotation angle of the rotor.

According to a fourth aspect of the invention, in the rotary detector ofthe first aspect, the rotary detector unit comprises a generator whichoutputs a voltage in accordance with the angle speed of the rotor.

According to a fifth aspect of the invention, in the rotary detector ofthe first aspect, the rotary detector unit comprises an encoder whichcreates an output in accordance with the rotation angle of the rotor.

According to a sixth aspect of the invention, in the rotary detector ofthe first aspect, the rotary detector unit is provided separate from therotary calculator unit.

According to a seventh aspect of the invention, in the rotary detectorof the first aspect, the rotary detector unit houses the rotarycalculator unit.

According to an eighth aspect of the invention, in the rotary detectorof the first aspect, the rotary calculator unit comprises a unit forreducing a ripple component of the angle speed.

According to a ninth aspect of the invention, in the rotary detector ofthe first aspect, the rotary calculator unit calculates an angle speedω_(out) by calculatingω_(out)=ω(1−G·sin (nθ+Ψ)

-   -   where θ represents the rotation angle, G represents the gain of        the gain adjuster, Ψ represents the adjust phase value of the        phase adjuster, and n represents the number of ripple cycles in        the output of the rotary angle detector in one rotation of the        rotor.

According to a tenth aspect of the invention, in the rotary detector ofthe first aspect, the rotary calculator unit comprises a unit forreducing a ripple component of the rotation angle.

According to an eleventh aspect of the invention, in the rotary detectorof the first aspect, the rotation angle detector comprises an integratorwhich obtains a rotation angle by integrating the output of the anglespeed detector.

According to a twelfth aspect of the invention, in the rotary detectorof the first aspect, the rotary calculator unit comprises an integratorfor integrating the angle speed output ω_(out).

According to a thirteenth aspect of the invention, in the rotarydetector of the first aspect, the rotary calculator unit outputs arotation angle signal which reduces the ripple component of the rotationangle, and an angle speed signal which reduces the ripple component ofthe angle speed.

According to a fourteenth aspect of the invention, in the rotarydetector of the first aspect, the rotary calculator unit is provided inseries in a plurality of levels.

According to a fifteenth aspect of the invention, in the rotary detectorof the second aspect, the phase adjuster has a plurality of adjust phasevalues, and selectively outputs one of the plurality of adjust phasevalues in accordance with a direction of the torque acting on the rotor.

According to a sixteenth aspect of the invention, in the rotary detectorof the first aspect, the gain adjuster varies the predetermined gain inaccordance with external power in the gravitational direction acting onthe rotor rotation axis of the rotor.

Principles

This invention can effectively eliminate the ripple component in theoutput of a rotary detector unit, and particularly the ripple componentwhich is dependent on the rotation cycle of the device being measured.When the output of the rotary detector unit contains a plurality ofripple components, all the ripple components can effectively beeliminated by provided a plurality of rotary calculators incorrespondence with the ripples. That is, when θ_(o) represents therotation angle of the device being detected, the output of a rotarydetector unit having a ripple with an amplitude of a is converted by arotation angle detector to the rotation angle output θ of the followingequation.θ=θ_(o) −a·cos(nθ _(o)+φ)  (2)

-   -   where n represents the number of ripple cycles in one rotation        of the device being detected, and φ represents the initial phase        difference when attaching the rotary detector unit to the device        being detected.

In the present invention, for example, when an angle speed detectortime-differentiates the rotation angle output θ, the following anglespeed output ω is obtained.ω=dθ _(o) /dt(1+a·n·sin(nθ _(o)+φ))  (3)

When a rotary calculator unit calculates the output ω_(out) of the unitbased, for example, on equation (1), the output ω_(out) is expressed bysubstituting equations (2) and (3) for equation (1) as follows

$\begin{matrix}{\omega_{out} = {{\mathbb{d}\theta_{o}}/{\mathbb{d}{t\left( {1 - {G \cdot {\sin\left( {\Psi - {a \cdot n \cdot {\cos\left( {{n\;\theta_{o}} + \phi} \right)}} + {n\;\theta_{o}}} \right)}} + {a \cdot n \cdot {\sin\left( {{n\;\theta_{o}} + \phi} \right)}} - {{a \cdot n \cdot G \cdot {\sin\left( {\Psi - {a \cdot n \cdot {\cos\left( {{n\;\theta_{o}} + \phi} \right)}} + {n\;\theta_{o}}} \right)}}{\sin\left( {{n\;\theta_{o}} + \phi} \right)}}} \right)}}}} & (4)\end{matrix}$Here, dθ_(o)/dt represents the angle speed of the device being detected.

In equation (4), since the ripple amplitude is generally small so that a<<1, when a trigonometrical function is developed in a near-linear formnear an angle of zero, the equation becomes

$\begin{matrix}{{{\omega_{out} = {{\mathbb{d}\;\theta_{0}}/{\mathbb{d}{t\left( {1 - {G \cdot {\sin\left( {\Psi + {n\;\theta_{o}}} \right)}} + {{a \cdot n \cdot G \cdot {\cos\left( {\Psi + {n\;\theta_{o}}} \right)}}{\cos\left( {{n\;\theta_{o}} + \phi} \right)}} + {a \cdot n \cdot {\sin\left( {{n\;\theta_{o}} + \phi} \right)}} - {{a \cdot n \cdot G \cdot {\sin\left( {\Psi - {a \cdot n \cdot {\cos\left( {{n\;\theta_{o}} + \phi} \right)}} + {n\;\theta_{o}}} \right)}}{\sin\left( {{n\;\theta_{o}} + \phi} \right)}}} \right)}}}}{{{{Assuming}\mspace{20mu}{a \cdot G}} = 0},{then}}}\mspace{481mu}} & (5) \\{\omega_{out} = {{\mathbb{d}\theta_{o}}/{\mathbb{d}{t\left( {1 - {G \cdot {\sin\left( {{n\;\theta_{o}} + \Psi} \right)}} + {a \cdot n \cdot {\sin\left( {{n\;\theta_{o}} + \phi} \right)}}} \right)}}}} & (6)\end{matrix}$Equation (6) shows that, when the gain G of in equation (1) can be setequal to the proportion of ripples a·n, and the adjust phase Ψ can beset equal to the initial phase difference φ, the output ω_(out) of therotary calculator unit is equal to the angle speed dθ_(o)/dt of thedetected device, and the ripple component in the output of the rotationangle detector unit can be eliminated.

Furthermore, error between the output ω_(out) of the rotary calculatorunit and the angle speed dθ_(o)/dt can be determined from Equation (6)as

$\begin{matrix}{e_{rr} = {{\omega - {{\mathbb{d}\theta_{o}}/{\mathbb{d}t}}} = {\left( {{a \cdot n \cdot {\sin\left( {{n\;\theta_{o}} + \phi} \right)}} - {G \cdot {\sin\left( {{n\;\theta_{o}} + \Psi} \right)}}} \right){{\mathbb{d}\theta_{o}}/{\mathbb{d}t}}}}} & (7)\end{matrix}$which can be expanded to

$\begin{matrix}{e_{rr} = {{{\mathbb{d}\theta_{o}}/{\mathbb{d}t}}\sqrt{\left( {{a^{2}n^{2}} + G^{2} - {2\mspace{11mu}{anG}\mspace{11mu}{\cos\left( {\psi - \phi} \right)}}} \right)} \times {\sin\left( {{n\;\theta_{o}} + \phi - {\tan^{- 1}\frac{G\mspace{11mu}{\sin\left( {\psi - \phi} \right)}}{{an} - {G\mspace{11mu}{\cos\left( {\psi - \phi} \right)}}}}} \right)}}} & (8)\end{matrix}$

The amplitude of the error err is a concave function having its onlyminimum point at zero with respect to, for example, a gain G of between0 to 2 an, and an adjust phase Ψ of between −π+φ+ to π+φ+; the minimumvalue of zero can easily be determined from appropriate values for G andΨ. When the proportion of ripples an and the initial phase φ are knownin advance, G and Ψ should of course be set to their known values fromthe start.

In this way, the present invention is able to reduce the output ripplesof a rotary detector, and can also reduce torque ripples and speedirregularities in an actuator such as a rotor, which the rotary detectoris installed in. Further, since the output ripple can be determined bythe simple computation of Equation (1), the drive device and controldevice for the actuator can be simplified and cost can be lowered. As isclear from Equation (8), when the amplitude of the error err is zero,the ripple component can be reduced irrespective of the rotation speedof the detected device, increasing the precision and reliability of therotary detector.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of the overall constitution of a firstembodiment of this invention;

FIG. 2 is a block diagram showing the overall constitution of the firstembodiment;

FIG. 3 is a pattern diagram showing the relationship between targetangle speed and time in the first embodiment;

FIG. 4 is a pattern diagram showing the relationship between torquecommand value and time in the first embodiment;

FIG. 5 is a pattern diagram showing the relationship between torquecommand value and time in a conventional device;

FIG. 6 is a perspective view showing a modification of the rotarydetector in the first embodiment;

FIG. 7 is a perspective view showing another modification of the rotarydetector in the first embodiment;

FIG. 8 is a perspective view of the overall constitution of a secondembodiment of this invention;

FIG. 9 is a block diagram showing the overall constitution of the secondembodiment;

FIG. 10 is a perspective view of the overall constitution of a thirdembodiment of this invention; and

FIG. 11 is a block diagram showing the overall constitution of the thirdembodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present invention will be explained in detail withreference to the accompanying drawings.

Embodiment 1

A first embodiment of this invention will be explained with reference toFIGS. 1 to 7.

In FIGS. 1 and 2, reference code 1 represents the overall rotarydetector in a first embodiment. The rotary detector 1 comprises a rotarydetector unit C1, and rotary calculator units C2 and C2′.

The rotary detector unit C1 of this embodiment is attached to the devicebeing detected, here comprising a rotor rotating axis 13 of a rotaryelectric motor 11, and comprises a resolver 15 which outputs a voltageproportionate to the rotation angle of the rotor rotation axis 13, arotation input axis 17 which is directly connected to an unillustratedrotor of the resolver 15, and a rotation transmitting unit 19 whichconnects to the rotor rotation axis 13 and transmits rotations of therotor rotation axis 13 to the rotation input axis 17 of the resolver 15.

The rotation transmitting unit 19 comprises, for example, a universaljoint and a coupler, and the rotation input axis 17 of the resolver 15ideally rotates around an axis core which matches that the rotorrotation axis 13. The resolver 15 comprises an unillustrated rotor whicha winding is wound around and a stater 21 having a similar winding; inaddition, the resolver 15 comprises a signal processor 23 which outputsa voltage corresponding to the rotation angle of each rotation angle of0 to 2π (rad) of the rotation input axis 17 from a predetermined pointof origin, e.g. a voltage of 0 to 5 V. The stater 21 of the resolver 15is secured on a board 25 by a supporting member 27 using a predeterminedmethod.

The device being detected, in this case the rotary electric motor 11,will be explained. The rotary electric motor 11 is secured by stoppers31, mounted on a base 29, and as a result becomes one piece with thebase 29. In addition to the rotor rotation axis 13, the rotary electricmotor 11 comprises a stater housing 33 which houses the stater of therotary electric motor 11, a bearing 35 which can rotatably support therotor rotation axis 13 at the cylindrical bottom face center portion ofthe 33, a pulley 37 which is attached to the output side of the rotorrotation axis 13 and transmits power to the negative load of the rotaryelectric motor 11 by an unillustrated predetermined method, a speedcontrol device 39 which calculates a torque command value forcontrolling the rotation speed of the rotor rotation axis 13 based onthe output of the rotary detector 1, and a drive device 43 which iselectrically powered by a three-phase alternating power 41 and, based onthe output of the speed control device 39, generates a torque equivalentto the torque command value for the rotor rotation axis 13.

The output signal of the rotary detector unit C1 is input to the rotarycalculator unit C2. This output signal contains a first ripplecomponent, which fluctuates at the rotation cycle of the rotor rotationaxis 13 and is caused by installation displacement differences and thelike of the rotation transmitting unit 19, and a second ripplecomponent, which fluctuates at an integral multiple (e.g. four) of therotation cycle of the rotor rotation axis 13 and is caused byelectromagnetic action of the uneven wind of the unillustrated windingof the resolver 15. The rotary calculator unit C2 and rotary calculatorunit C2′ are provided in order to reduce these ripples and obtainsignals which correspond accurately to the detected rotation angle. Therotary calculator unit C2 comprises a rotation angle detector 45 whichconverts the signal output from the signal processor 23 to a rotationangle signal of the rotor rotation axis 13, an angle speed detector 47which converts the rotation angle signal to an angle speed signal of therotor rotation axis 13, a phase adjuster 49 which adjusts a phase anglewith respect to the output signal of the rotation angle detector 45, acycle number gain multiplier 51 which multiples the number of cycles ofripples to be eliminated from the output of the rotation angle detector45 in one rotation of the rotor rotation axis 13 (e.g. four) by an inputsignal, an adder 53 which adds the output of the phase adjuster 49 tothe output of the cycle number gain multiplier 51, a sine calculator 55which inputs the output from the adder 53 and calculates a sine value ofthe input value, a gain adjuster 57 which multiplies the output of thesine calculator 55 by an adjustable gain, a multiplier 59 whichmultiplies the output of the gain adjuster 57 by the output of the anglespeed detector 47, and a subtracter 61 which subtracts the output of themultiplier 59 from the output of the angle speed detector 47. The phaseadjuster 49, the cycle number gain multiplier 51, the adder 53, and thesine calculator 55 together form a trigonometrical calculator C3.

The rotary calculator unit C2′ comprises a rotation angle detector 45′as an integrator which integrates the angle speed comprising the outputof the rotary calculator unit C2, a phase adjuster 49′ which adjusts aphase angle with respect to the output signal of the rotation angledetector 45′, an adder 53′ which adds the output of the phase adjuster49′ to the output of the rotation angle detector 45′, a sine calculator55′ which inputs the output from the adder 53′ and calculates a sinevalue of the input value, a gain adjuster 57′ which multiplies theoutput of the sine calculator 55′ by an adjustable gain, a multiplier59′ which multiplies the output of the gain adjuster 57′ by the outputof the rotary calculator unit C2, and a subtracter 61′ which subtractsthe output of the multiplier 59′ from the output of the rotarycalculator unit C2, and an integrator 63′ which integrates the anglespeed comprising the output of the subtracter 61′. The phase adjuster49′, the adder 53′, and the sine calculator 55′ together form atrigonometrical calculator C3′.

To facilitate understanding, the speed control device 39 and the drivedevice 43 will be explained. The speed control device 39 comprises anangle speed target pattern generator 65 which outputs an angle speedtarget pattern to be followed by the angle speed of the rotor rotationaxis 13, and a torque command calculator 67 which calculates a torquecommand value for the rotation speed of the rotor rotation axis 13 tochase the target pattern at, based on the output of the angle speedtarget pattern generator 65 and the angle speed output of the subtracter61′ of the rotary calculator unit C2′. The drive device 43 comprises aconverter 69 which converts ac power from the three-phase alternatingpower 41 to dc power, and an inverter 71 which inputs the dc power fromthe converter 69 and outputs a predetermined three-phase ac power suchthat the rotary electric motor 11 generates a torque which is equivalentto the torque command value, based on the output of the torque commandcalculator 67 and the output of the integrator 63′. The inverter 71comprises a firing angle controller 73 which controls a thyristor firingangle based on the outputs of the torque command calculator 67 and theintegrator 63′ so that a three-phase ac current for generating thedesired torque is supplied to the rotary electric motor 11, and athyristor section 75 which supplies the three-phase ac current to therotary electric motor 11 in compliance with the output from the firingangle controller 73.

In the rotary detector 1, the speed control device 39, and the drivedevice 43, the power needed for the operations of these devices issupplied from a single-phase ac power 77. Incidentally, in the blockdiagrams below, the arrow lines represent signal paths, and the solidlines present power paths near the rotary electric motor 11 and therotary detector 1.

Subsequently, the operation of the rotary detector according to theembodiment described above will be explained.

When the device is in standby (that is, when the three-phase alternatingpower 41 and the single-phase ac power 77 are injected and the rotarydetector 1, the speed control device 39, and the drive device 43 are inoperation status but the angle speed target pattern generator 65 isoutputting zero), the rotor rotation axis 13 maintains an angle speed ofzero. Eventually, when the angle speed target pattern generator 65generates a mount-shaped pattern, such as that shown for example in FIG.3, and the target angle speed starts to increase, the torque commandcalculator 67 calculates the torque command value to be generated by therotary electric motor 11 based on the present angle speed of the rotorrotation axis 13 output from the subtracter 61′ and the angle speedtarget value of the angle speed target pattern generator 65, and thecalculated result is output to the drive device 43. Then, the firingangle controller 73 controls the firing angle to the j75 so that therotary electric motor 11 generates the torque specified by the commandvalue, and the output current of the inverter 71 rotates the rotaryelectric motor 11 at a predetermined rotation speed at the torquespecified by the command value. In this way, the torque generated by therotary electric motor 11 starts to rotate the pulley 37 and the rotorrotation axis 13.

The rotation of the rotor rotation axis 13 is transmitted via therotation transmitting unit 19 and the rotation input axis 17 to theresolver 15, and the output voltage at the signal processor 23 increasesin correspondence with the increase in the rotation angle of the rotorrotation axis 13. Based on the output voltage of the signal processor23, the rotation angle detector 45 detects the rotation angle of therotor rotation axis 13, and the angle speed detector 47 detects theangle speed via, for example, a differentiator or the like. At thistime, the output voltage of the signal processor 23 contains a firstripple and a second ripple for the reasons described above.

With respect to the rotation angle obtained by the rotation angledetector 45, the cycle number gain multiplier 51 multiplies the numberof ripple cycles in one rotation of the rotor rotation axis 13 by, inthis example, four, and the adder 53 adds to this the predeterminedphase angle of the phase adjuster 49 and inputs it to the sinecalculator 55, which calculates a sine value of the value output fromthe adder 53. The gain adjuster 57 multiplies the output of the sinecalculator 55 by a predetermined gain, and the multiplier 59 multipliesthe output of the gain adjuster 57 by the angle speed from the anglespeed detector 47. The output of the multiplier 59 and the angle speedfrom the angle speed detector 47 are applied to the subtracter 61, whichsubtracts the output of the multiplier 59 from the output of the anglespeed detector 47; the result becomes the output of the rotarycalculator unit C2. That is, with respect to the rotation angle andangle speed of the rotor rotation axis 13, the result calculated in theequation (1) is output from the rotary calculator unit C2 as the anglespeed. Therefore, the second ripple component is eliminated at the anglespeed output from the rotary calculator unit C2.

The angle speed output from the rotary calculator unit C2 is then inputto the rotary calculator unit C2′. Here, the rotation angle detector 45′comprising the integrator integrates the angle speed and converts it toa rotation angle. The phase adjuster 49′ obtains a predetermined phaseangle corresponding to the initial phase angle of the first ripplecomponent, and the rotation angle detector 45′ and the phase adjuster49′ both output to the adder 53′. The cycle number gain multiplier 51,provided between the rotation angle detector 45′ and the adder 53′, isnot provided in the rotary calculator unit C2 because the first ripplecomponent to be eliminated is in synchronism with the rotor axis ofrotation. The sine calculator 55′ calculates a sine value for therotation angle output by the adder 53′, and the gain adjuster 57′multiplies the value output from the sine calculator 55′ by apredetermined gain, corresponding to the amplitude of the first ripplecomponent. The multiplier 59′ multiplies the output from the gainadjuster 57′ by the angle speed output from the rotary calculator unitC2, and the subtracter 61′ subtracts the output of the multiplier 59′from the angle speed output from the rotary calculator unit C2. That is,the result calculated in the first equation (1) is output from thesubtracter 61′ as the angle speed for the first ripple component.Therefore, all the ripple components are eliminated at the angle speedoutput from the subtracter 61′. The angle speed output from thesubtracter 61′ is applied as a first output of the rotary calculatorunit C2′ to the speed control device 39, and is applied to theintegrator 63′ and converted to a rotation angle. The rotation angleoutput of the integrator 63′ is input to the drive device 43 as theoutput of the rotary calculator unit C2′. The rotation angle and anglespeed of the rotor rotation axis 13 increase as the angle speed targetvalue increases, and are input accurately to the torque commandcalculator 67 and the firing angle controller 73, so that no abnormalvibrations accompanying the increase in angle speed, or torque rippleswhen the angle speed is constant, are generated in the output of therotary electric motor 11, and the pulley 37 rotates at an angle speedwhich closely follows the angle speed target pattern shown in FIG. 3.When the target angle speed eventually reaches zero, the angle speed ofthe pulley 37 also becomes zero, and the rotary electric motor 11returns to standby status.

In this case, the torque command value of the torque command calculator67 has the waveform shown in FIG. 4 (corresponding to the differentialvalue of the speed pattern of FIG. 3), but when the rotation informationof the rotor rotation axis 13 is input directly from the rotary detectorunit C1 to the speed control device 39 as in a conventional apparatus,as the angle speed of FIG. 3 increases, ripples are generated in thetorque command, as shown in FIG. 5. The frequency and amplitude of theripples increase until the angle speed of the rotor rotation axis 13 hasincreased to its maximum, and disappear as the angle speed finallydecreases. When there are ripples in the torque command from zero untilthe frequency when operating at maximum angle speed, resonance may beexcited at a specific frequency in the system connected to the rotaryelectric motor 11. While resonance is being excited in the system, whenthe rotor rotation axis 13 reaches a specific angle speed, the systemgenerates noise and vibrations which are potentially damaging to thesystem itself. To prevent this and increase the reliability of thesystem, the rigidity of the overall system comprising the rotaryelectric motor 11 is increased to raise the resonance frequency.However, since very strong materials and reinforcements are needed toincrease the rigidity of the system, the result is an increase in thecost of the overall system connected to the rotary electric motor 11. Incontrast, as shown in FIG. 4, this embodiment has no ripples in thetorque, and consequently has no problem of increased cost.

Incidentally, although rotary detector of the first embodiment comprisesthe resolver 15, there are no restrictions on its constitution andvarious modifications are possible. For example, a generator whichobtains an output voltage proportionate to the angle speed of therotation input axis 17 is equally acceptable. Furthermore, although therotation of the rotary electric motor 11 is transmitted by the rotationtransmitting unit 19 and the rotation input axis 17, this does not implyrestriction to the use of the rotation transmitting unit 19 and therotation input axis 17. As shown by way of example in FIG. 6, the rotarydetector unit C1 may comprise an optical encoder 83 wherein a stripepattern 79 at equal intervals is provided around the end of the rotorrotation axis 13, and is read by an optical element 81 contained in asignal processor 23′. Alternatively, as shown in FIG. 7, the rotation ofthe rotor rotation axis 13 can be transmitted to a rotary encoder via arotation transmitting unit comprising a roller 85.

Embodiment 2

Subsequently, a second embodiment of this invention will be explainedwith reference to FIGS. 8 and 9.

In the first embodiment, the output signal of the rotary detector unitC1 is processed by the rotary calculation units C2 and C2′, which areprovided in series. However, there are no restrictions on the number andconstitution of rotary calculation units, which may be modified inaccordance with the features of the ripple component in the signaloutput by the rotary detector. For example, in a rotary detector unitC1′ comprising a rotary encoder 87 instead of the j15, there is nosecond ripple component caused by the j15. On the other hand, when thereis backlash in the rotation transmitting unit 19 comprising a coupling,the adjust phase fluctuates in accordance with the torque direction ofthe rotary electric motor 11. When the negative load of the rotaryelectric motor 11 exerts an external force against the rotor rotatingaxis 13 in a direction warping the axis core, deviation in compliancewith the size of the negative load occurs between the axis core of therotor rotating axis 13 and the axis core of the j17 connected to anunillustrated rotating axis of the rotary encoder 87, whereby theamplitude of the ripple component fluctuates. In such a case, a rotarycalculator unit C2″ should be used which comprises a phase adjuster 49″capable of changing the adjust phase value by using positive andnegative codes of the output of the torque command calculator 67, and again adjuster 57″ capable of detecting the external force in the warpdirection of the axis core and changing the supplementary gain by acorresponding amount. FIGS. 8 and 9 shows an example of such anembodiment.

The rotary calculator unit C2″ comprises a phase adjuster 49″, a gainadjuster 57″, and a code determining unit 89 which inputs the signalfrom the torque command calculator 67 and determines whether it isnegative or positive. The code determining unit 89 outputs to the phaseadjuster 49″, which outputs predetermined initial phase values based onwhether the output of the torque command calculator 67 is positive ornegative. When an external force in the gravitational direction warpsthe axis core of the rotor rotating axis 13, the gain of the gainadjuster 57″ is increased or reduced based on the output of an externalforce detecting unit 93, and the gain is adjusted to a value equal tothe amplitude of the first ripple component described above. Theexternal force detecting unit 93 comprises four load cells 91, which areprovided between an unillustrated floor surface and the four corners ofthe base 29 and output voltage signals in accordance with the force inthe gravitational direction, and an external force calculator unit 95which calculates the external force in the gravitational direction fromthe outputs of the load cells 91; the external force calculator unit 95outputs a calculation of the external force. That is, no matter what theoperating environment of the rotary detector 1, the code determiningunit 89 and the external force detecting unit 93 ensure that the errorerr in Equation (8) is zero. The gain of the cycle number gainmultiplier 51 in the rotary calculator unit C2″ is of course set to 1.In this embodiment, the trigonometrical calculation unit C3″ comprisesthe phase adjuster 49″, the cycle number gain multiplier 51, the adder53, and the sine calculator 55.

Embodiment 3

A third embodiment of this invention will be explained with reference toFIGS. 10 and 11.

In the first and second embodiments, the rotary detection units (C1 andC1′) are adjacent to the rotary calculation units (C2, C2′, and C2″),and together form the overall rotary detector 1, but there are norestrictions on the distance and positions of the rotary detection unitsand rotary calculation units. As shown in FIGS. 10 and 11, the rotarycalculator unit C2 may be incorporated in the speed control device 39and the drive device 43. Since the drive device 43′ requires rotationangle information, the output of the rotary calculator unit C2 is inputvia the integrator 63′ to the firing angle controller 73. The rotarycalculator unit C2′ is not used here, since the first ripple componentcaused by the rotary transmitting unit is negligible. In thisembodiment, the rotary detector unit C1 may be installed in the rotaryelectric motor 11, achieving an advantage of simple installation.

In the embodiments described above, the rotary calculation units C2,C2′, and C2″ are analog calculation systems, but the constitution is notrestricted to analog calculation and digital calculation is acceptable.

In the embodiments described above, the detected device is a rotaryelectric motor, but there are no restrictions on the device detected bythe rotary detector. For example, the detected device may be a rotor, apower generator, a linear motor which uses a rotary encoder to convert alinear distance moved by a movable element via wheels to a rotationangle.

In addition to the above, various other modifications may be made withinthe scope of the invention.

As described above, according to the rotary detector of this invention,the ripple component in an output signal caused by the rotary detectoritself can be greatly reduced, making it possible to reduce torqueripples of an electric motor and various types of actuators, generatedby the rotation angle detector unit, and to increase the controlperformance of these actuators.

Further, since the torque ripple caused by the rotary detector unit canbe eliminated, it becomes easier to identify the causes of torqueripples caused by other factors.

Further, since the output ripples of the rotary detector unit can bedetermined by a simple calculation, the drive and control devices of theactuator can be simplified and their cost can be reduced.

Moreover, since the ripple component can be reduced irrespective of therotating speed of the detected device, the precision and reliability ofthe rotary detector unit can be increased.

1. A rotary detector comprising: a rotary detector unit which detectsrotary motion of a rotor; and a rotary calculator unit comprising arotation angle detector, which detects a rotation angle of said rotor,and an angle speed detector which detects an angle speed of said rotor,based on an output of said rotary detector unit; said rotary calculatorunit comprising: a trigonometrical calculator which calculates a sinevalue or a cosine value of the rotation angle detected by said rotarydetector; a gain adjuster which multiplies the sine value or the cosinevalue, calculated by said trigonometrical calculator, by a predeterminedgain; a multiplier which multiplies an output of said gain adjuster byan output of said angle speed detector; and a subtracter which subtractsan output of said multiplier from the output of said angle speeddetector.
 2. The rotary detector as described in claim 1, saidtrigonometrical calculator comprising a phase adjuster which adjusts aphase of the rotation angle, detected by said rotation angle detector.3. The rotary detector as described in claim 2, said rotary calculatorunit calculating an angle speed ω_(out) by calculatingω_(out)=(1−G·sin(nθ+Ψ) where θ represents the rotation angle, Grepresents the gain of the gain adjuster, Ψ represents an adjust phasevalue of the phase adjuster, and n represents a number of ripple cyclesin the output of said rotary angle detector in one rotation of saidrotor.
 4. The rotary detector as described in claim 2, said phaseadjuster having a plurality of adjust phase values, and selectivelyoutputting one of said plurality of adjust phase values in accordancewith a torque code of said rotor.
 5. The rotary detector as described inclaim 1, said rotary detector unit comprising a resolver which createsan output in accordance with the rotation angle of said rotor.
 6. Therotary detector as described in claim 1, said rotary detector unitcomprising a generator which outputs a voltage in accordance with theangle speed of said rotor.
 7. The rotary detector as described in claim1, said rotary detector unit comprising an encoder which creates anoutput in accordance with the rotation angle of said rotor.
 8. Therotary detector as described in claim 1, said rotary detector unit beingprovided separately from said rotary calculator unit.
 9. The rotarydetector as described in claim 1, said rotary detector unit housing saidrotary calculator unit.
 10. The rotary detector as described in claim 1,said rotary calculator unit comprising a unit for reducing a ripplecomponent of said angle speed.
 11. The rotary detector as described inclaim 1, said rotary calculator unit comprising a unit for reducing aripple component of said rotation angle.
 12. The rotary detector asdescribed in claim 1, said rotation angle detector comprising anintegrator which obtains a rotation angle by integrating an output ofsaid angle speed detector.
 13. The rotary detector as described in claim1, said rotary calculation unit comprising an integrator for integratingsaid angle speed output ω_(out).
 14. The rotary detector as described inclaim 1, said rotary calculator unit outputting a rotation angle signalwhich reduces a ripple component of said rotation angle, and an anglespeed signal which reduces a ripple component of said angle speed. 15.The rotary detector as described in claim 1, said rotary calculator unitbeing provided in series in a plurality of levels.
 16. The rotarydetector as described in claim 1, said gain adjuster varying saidpredetermined gain in accordance with an external force in thegravitational direction acting on rotor rotation axis of said rotor.